. >> reporter: romney's running mate paul ryan was greeted by his family in iowa before kicking off a bus tour in dubuque where he emphasized the importance of the upcoming debates. >> we are entering the debate phase, the choice phase of this campaign, and this choice is ever so clear. >> reporter: president obama is hunkering down in nevada preparing for his one-on-one confrontation with romney, keeping a much more low key pre-debate schedule in a las vegas suburb. the president did make a brief appearance at a local campaign office where he delivered pizzas and called and thanked volunteers. >> the work that you're doing is making all the difference. >> reporter: and he joked about how he's preparing for the debate. >> basically they are keeping me indoors all the time. it's a drag. they are making me do my homework. >> reporter: while romney aides continue to play down expectations for the debate, new jersey governor chris christie continued to ramp them up on monday. >> it's a huge night. had a bad couple of weeks, and we want to turn this around, and if you want to turn it aroun